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Engineering a Self-Healing Living Material

This highly processable, programmable, and self-healable living functional material may find applications in biomanufacturing and bioremediation.

Recently, a team of scientists from the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences reported the programmed self-assembly by engineered adhesion.

Natural organisms produce living material that can process signals, trigger cascade reactions, and heal themselves. Inspired by nature, engineered living materials can act as functional materials mimicking the desirable properties of natural living systems.

Most efforts in developing these materials have been in biofilm engineering, where bacterial biofilms containing living cells can generate and be embedded within an extracellular matrix, making it an attractive property for self-healing. However, this self-healing process, which is theorised to be caused by cell growth that can take hours, needs to occur within minutes if it is to be used for soft and conformable devices.

Previous studies have reported that by incorporating non-covalent interactions such as hydrogen bonds, we can engineer fast self-healing materials. Based on this strategy, the team sought to functionalise each bacterium with non-covalent binding groups to produce macroscopic living functional materials by adhering bacteria together.

Based on a previous work done by David S. Glass and colleagues, who developed a synthetic bacterial cell-cell adhesion toolbox based on outer membrane-anchored nanobody (Nb)-antigen (Ag) pairs, the team from Shenzhen Institute of Advanced Technology used this toolbox to engineer cells to display Nb or Ag on their surfaces and cultured these cells separately in liquid cultures. By mixing the two populations of cells together, the team produced these macroscopic materials called “living assembled material by bacterial adhesion” (LAMBA).

LAMBA was shown to possess better mechanical properties and processability than individual cells (Nb-cells or Ag-cell) and can work with different engineering methods to fabricate macro or microscale objects.

By functionalising LAMBA extracellularly and intracellularly, their material can undergo a hybrid enzyme-inorganic sequential catalysis and degrade organophosphate pesticides or utilise extracellular-intracellular bioconversions to synthesise trehalose.

The LAMBA can also self-heal, but apart from the self-healing process that is led by cell growth, adhesion between Nb-Ag pairs can also lead to recovery of the material property in a few minutes. For instance, sliced LAMBA is found to maintain its conductivity under multiple cycles of stretching after it has recovered. This property could address the fatigue issue that is often observed in wearable devices. To this end, the team assembled stretchable LAMBA sensors to detect bioelectrical or biomechanical signals. The obtained results revealed that while a traditional stretchable sensor made of gold film lost function easily due to the large deformation of the finger joint, the stretchable LAMBA strain sensor was able to report a finger joint bending in a stable and reliable manner.

Their study established a novel methodology for utilising bacterial adhesion to yield a highly processable, programmable, and self-healable living functional material in a fast and scalable manner. With these advantages in mind, the team look forward to exploring its application in biomanufacturing, bioremediation, and bioelectronics. [APBN]

Source: Chen et al. (2021). Programmable living assembly of materials by bacterial adhesion. Nature chemical biology, 1-6.